It seems that the distutils_install_for_testing call used to install virtualenv-16 locally is leaking files into ${BUILD_DIR}/lib where they are afterwards picked up by `setup.py install`.
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=ce90f1cf81154f8c0dda353bf6a3ddeaf1249dc3 commit ce90f1cf81154f8c0dda353bf6a3ddeaf1249dc3 Author: Michał Górny <mgorny@gentoo.org> AuthorDate: 2022-01-31 08:17:16 +0000 Commit: Michał Górny <mgorny@gentoo.org> CommitDate: 2022-01-31 08:31:26 +0000 dev-python/pip: Fix accidentally installing virtualenv w/ USE=test Closes: https://bugs.gentoo.org/832402 Signed-off-by: Michał Górny <mgorny@gentoo.org> dev-python/pip/pip-21.3.1-r1.ebuild | 2 ++ dev-python/pip/pip-22.0.1.ebuild | 2 ++ 2 files changed, 4 insertions(+)